Tech: S550 Cradle Bushing Lockout Kit

Lock the Cradle

The elegant independent rear suspension under the latest Mustang delivers the handling and ride quality that sets the latest car apart from its predecessors However, to meet Ford’s stringent noise, vibration, and harshness standards, soft bushings are necessary to tune out those bumps and buzzes that average drivers will complain about.

This is the complete Cradle Bushing Lockout Kit (PN CB005; $ $159.95), which is made up of four CNC-machined upper bushing lockout rings, two steel lower bushing support washers, two CNC-formed stainless lower bushing support plates, and two cradle braces. They combine to lock the cradle in place without the hassle of removing the factory bushings.

Some of those soft bushings help isolate the IRS cradle from the chassis. That’s all well and good until you start to drive your new Mustang in anger. Drop the hammer and those bushings give. The cradle moves around, the wheels hop, and the suspension geometry changes. These conditions are less than ideal, especially if you are trying to maximize quarter-mile or lap times.

Fortunately there are clever folks in the aftermarket dedicated to sharpening the suspension of our Mustangs. One such outfit is BMR Suspension. We recently gave you a look inside the company’s comprehensive product development for the S550 platform. In that story we showed you just how much the cradle moves around based on the markings left on the chassis. We also teased the company’s new cradle braces.

The cradle braces are available in BMR Suspensions’ two signature powercoat finishes—red and hammertone (shown here.)

Well, those braces just hit the market as part of the company’s new Cradle Bushing Lockout Kit (PN CB005; $159.95), which is an easy, bolt-on way to secure the cradle in your 2015-and-newer Mustang.

“We developed this kit to give enthusiasts a way to greatly reduce wheel hop and bushing deflection without having to replace the stock bushing and adding loads of unwanted NVH,” Pete Epple, Marketing Tech at BMR Suspension, explained.

As we noted in our prior story on BMR’s S550 development efforts, the company has put its 2015 Mustang test vehicles through their paces with stock gear and a variety of BMR prototype parts to arrive at production components that will get the job done.

These are the four upper bushing lockout rings. Built on CNC machines and powdercoated black, these rings simply fit over the top of the factory bushings to capture the inner sleeve of the factory bushing and the outer lip of the bushing cup on the cradle. The two lower bushing support plates (top) fit over the bottom of the rear bushings’ steel inserts.

“In our testing we have seen about an 80- to 90-percent reduction in fore/aft and lateral cradle bushing deflection. A car with no other mods and stock tires that isn’t driven overly hard is going to see a 90 percent or higher reduction, while a more race-oriented S550 with sticky tires that hits the tires harder will see slightly less of a reduction,” Pete explained. “Launching our test car at over 7,000 rpm on drag radials, we saw about an 80-percent reduction in bushing deflection. Through our testing we have seen a 95-percent or greater reduction in vertical deflection in all testing situations.”

That level of performance gain with an easy installation makes this kit quite a bargain at just over $150. However, percentages are one thing. The question is, what does the car feel like with the kit installed?

These lower bushing locating washers are designed to capture both the bottom of the inner sleeves and the factory rubber bushing thanks to the reliefs in the washers.

“With the CB005 installed, the rear of the car feels more connected than in stock trim. Before the car felt sloppy, and it was difficult to have any confidence,” BMR’s Ford Mustang Suspension Specialist Kelly Aiken elaborated. “The CB005 instantly adds more stability, giving you much less compliance, and higher levels of grip. We also saw significantly less wheel hop over the stock configuration. Through all of our testing, there has been a zero or near-zero gain in NVH.”

Starting in the rear you can remove the cradle bolts and let the cradle droop down.

According to BMR, the system can be installed in two hours or less using hand tools. Of course, if you want to see how the Cradle Bushing Lockout Kit installs, your friends at SVTP are here for you. We have the first installation photos of this simple solution for a more stable cradle.

And, if you are looking for your next move after installing this kit, Kelly has a few suggestions.

“With the CB005, the next modifications BMR would recommend are differential bushing, adjustable toe rods, spherical lower control arm bearings (currently in development), and vertical links,” he said. “These parts will make for one incredible S550!”

Then you can slip the upper bushing lockout rings over the top of the factory bushing, and install the lower bushing support plates with the stock bolts.With the rear supports in place, move to the front and remove the stock cradle bolts. Then slip over the upper bushing lockout rings over the stock bushings and install the lower bushing locating washers by sliding the bushing into the reliefs of the washer.Next, you can bolt on the cradle brace. The lug on the top of the cradle braces positively centers it on the chassis. When installed, the bottom also provides an extra jacking point.The cradle braces supplant the factory sheer plates and bolt to the chassis using two bolts, which ensures the brace is not budging.Here’s a look at the completed brace install. It’s hard to deny the cradle looks more secure now. After bolting on the kit, you will want to take your car in for a four-wheel alignment to make sure everything is within spec. Then you can torque the factory cradle bolts to 129 lb-ft so everything is locked into place.